1. Field of the Invention
The present invention relates to a light guide sensor which detects a curve by a change in light amount, and a method of forming the light guide sensor.
2. Description of the Related Art
A light guide sensor is generally known as a device which detects the bending and twisting of a flexible measurement target. The light guide sensor is, for example, a fiber sensor, and comprises a light source, an optical fiber having a core and a cladding which guide at least light, and a light receiving unit.
For example, Japanese Patent No. 4005318 has disclosed a flexible endoscope device comprising a curve detection optical fiber (detection light guide member) which is a fiber sensor having more than one curve detecting portion (optical characteristic converting portion). These optical characteristic converting portions are, for example, light absorption portions or light guide loss portions which are small defective portions where the core is exposed. The detection light guide member is disposed at a predetermined position on the surface of one flexible strip member extending in the longitudinal direction of an endoscope insertion portion. In this instance, the curve detecting portions are arranged at predetermined intervals in the longitudinal direction of the strip member, and the same curve detecting portions are arranged side by side in the lateral direction.
The optical characteristic converting portions formed in the detection light guide member have the function to lose light in accordance with the direction and degree of bending and twisting of an insertion portion flexible tube of a measurement target, for example, a flexible endoscope. That is, the direction and degree of bending are detected by the change of the light transmission amount in at least one optical characteristic converting portion arranged in the longitudinal direction. Moreover, in the event of twisting, the light transmission amount varies according to the successively arranged optical characteristic converting portions, and the direction and degree of twisting are detected by the variation of the light transmission amount.